In the construction and carpentry fields it is often necessary or desirable to lay out parallel lines which are to be the routes for pipes, wiring, conduits, conduit trays, or the like. These routes or lines are to be spaced throughout by a constant distance in order to maintain the lines parallel. The lines or sections of parallel lines must, at times, be turned or otherwise angularly diverted from a straight path, thereby to define sections which are offset but parallel with respect to each other and which are interconnected by intervening angled sections. The lines of the angled sections are likewise parallel to each other and spaced apart by the same constant distance. This, of course, means that one line of each of the straight sections adjoining an angled section must be extended to overlap the other line by a specific distance in order for all of the lines to be maintained parallel and spaced apart throughout by a constant distance.
A major problem rises from such a manner of construction because it is often difficult for a worker to determine the amount of overlap required in order to maintain the spacing and parallelism between the lines of each section. The determination of this overlap, in the past, has required the use of a protractor and trigonometric calculations as the amount of overlap between the lines is a function in the angle between an angled section and an adjoining straight section. Such trigonometric calculations of the overlap distance is often beyond the normal range of skill of the construction worker.
A further problem arising from the determination of this overlap distance is that a typical worker, while being most adept with linear measurements, is not so adept with angular measurements. Therefore, it is imperative that a worker be able to derive the requisite amount of overlap distance from linear measurements.